Showerhead electrode assemblies for plasma processing apparatuses

ABSTRACT

Showerhead electrode assemblies are disclosed, which include a showerhead electrode adapted to be mounted in an interior of a vacuum chamber; an optional backing plate attached to the showerhead electrode; a thermal control plate attached to the backing plate or to the showerhead electrode at multiple contact regions across the backing plate; and at least one interface member separating the backing plate and the thermal control plate, or the thermal control plate and showerhead electrode, at the contact regions, the interface member having a thermally and electrically conductive gasket portion and a particle mitigating seal portion. Methods of processing semiconductor substrates using the showerhead electrode assemblies are also disclosed.

BACKGROUND

In the field of semiconductor devices processing, semiconductor materialprocessing apparatuses including vacuum processing chambers, are used toperform various processes, such as etching and deposition of variousmaterials on substrates, and resist stripping. As semiconductortechnology evolves, decreasing device sizes, for example, transistorsizes, call for an ever higher degree of accuracy, repeatability andcleanliness in wafer processes and process equipment. Various types ofequipment exist for semiconductor processing, including applicationsthat involve the use of plasmas, such as plasma etch, plasma-enhancedchemical vapor deposition (PECVD) and resist strip and the like. Thetypes of equipment required for these processes include components whichare disposed within the plasma chamber, and must function in thatenvironment. The environment inside the plasma chamber may includeexposure to the plasma, exposure to etchant gasses, and thermal cycling.Materials used for such components must be adapted to withstand theenvironmental conditions in the chamber, and do so for the processing ofmany wafers which may include multiple process steps per wafer. To becost effective, such components must often withstand hundreds orthousands of wafer cycles while retaining their functionality andcleanliness. There is generally extremely low tolerance for componentswhich produce particles, even when those particles are few and no largerthan a few tens of nanometers. It is also necessary for componentsselected for use inside plasma processing chambers to meet theserequirements in the most cost-effective manner.

SUMMARY

An embodiment of a showerhead electrode assembly comprises a showerheadelectrode adapted to be mounted in an interior of a vacuum chamber andpowered by radio frequency (RF) energy; a backing plate attached to theshowerhead electrode; a thermal control plate attached to the backingplate via a plurality of fasteners at multiple contact regions acrossthe backing plate; and interface members separating the backing plateand the thermal control plate at the contact regions, wherein eachinterface member comprises a thermally and electrically conductivegasket portion bounded on a periphery by a particle mitigating sealportion.

An embodiment of a method of controlling plasma etching in a plasmaetching chamber comprises supplying process gas to the plasma etchingchamber through the showerhead electrode assembly, the process gasflowing into a gap between the showerhead electrode and a bottomelectrode on which a semiconductor substrate is supported; and etching asemiconductor substrate in the plasma etching chamber by applying RFpower to the showerhead electrode and energizing the process gas into aplasma state, wherein the temperature of the showerhead electrode iscontrolled by the thermal control plate via enhanced thermal conductionthrough the thermally and electrically conductive gasket portion of theinterface members. In the method, the above-described embodiment of theshowerhead electrode assembly can be used.

Another embodiment of a showerhead electrode assembly comprises ashowerhead electrode adapted to be mounted in an interior of a vacuumchamber; a thermal control plate attached to the showerhead electrode atmultiple contact regions across the showerhead electrode with plenumsbetween the thermal control plate and the showerhead electrode locatedbetween the contact regions; and an interface member separating theshowerhead electrode and the thermal control plate, at each of thecontact regions, wherein the interface member comprises a thermally andelectrically conductive gasket portion bounded on a periphery by aparticle mitigating seal portion.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an exemplary embodiment of a showerhead electrodeassembly of a semiconductor material plasma processing apparatus.

FIG. 2 is an enlarged view of a portion of the showerhead electrodeassembly shown in FIG. 1 including an embodiment of an interface member.

FIG. 3 is a schematic diagram of an embodiment of an interface member.

FIG. 4 is a plan view of an embodiment of an interface member.

FIGS. 5A-5C illustrate an embodiment of an interface member.

FIG. 6 is an enlarged view of a portion of a showerhead electrodeassembly shown in FIG. 1 including another embodiment of an interfacemember.

FIG. 7 illustrates a portion of a showerhead electrode assemblyaccording to another embodiment including an embodiment of an interfacemember.

FIG. 8 is an enlarged view of a portion of a showerhead electrodeassembly according to the other embodiment including another embodimentof an interface member.

DETAILED DESCRIPTION

Plasma processing apparatuses for semiconductor substrates, such assilicon wafers, include plasma etch chambers which are used insemiconductor device manufacturing processes to etch such materials assemiconductors, metals and dielectrics. For example, a dielectric etchchamber might be used to etch materials such as silicon dioxide orsilicon nitride. During the etch process, components within the etchchamber heat up and cool down and experience thermal stresses as aresult. For actively heated components of a heated showerhead assembly,this temperature cycling can result in increased particle generation.

A showerhead electrode assembly having a heater to prevent theshowerhead electrode from falling below a minimum temperature isdescribed in commonly-owned U.S. Patent Publication No. 2005/0133160A1,the disclosure of which is hereby incorporated by reference in itsentirety. The heater cooperates with a thermal control plate in heattransfer with a temperature controlled top plate which forms a top wallof a plasma etch chamber.

FIG. 1 depicts one-half of a showerhead assembly 100 of a parallel platecapacitively-coupled plasma chamber (vacuum chamber) comprising a topelectrode 103 and an optional backing member 102 secured to the topelectrode 103, a thermal control plate 101, and a top plate 111. Thermalchokes 112 can be provided on the upper surface of the thermal controlplate 101. The top electrode 103 is positioned above a substrate support160 supporting a semiconductor substrate 162, e.g., semiconductor wafer.

The top plate 111 can form a removable top wall of the plasma processingapparatus, such as a plasma etch chamber. As shown, the top electrode103 can include an inner electrode member 105, and an optional outerelectrode member 107. The inner electrode member 105 is typically madeof single crystal silicon. If desired, the inner and outer electrodes105, 107 can be made of a single piece of material such as CVD siliconcarbide, single crystal silicon or other suitable material.

The inner electrode member 105 can have a diameter smaller than, equalto, or larger than a wafer to be processed, e.g., up to 200 mm. Forprocessing larger semiconductor substrates such as 300 mm wafers, theouter electrode member 107 is adapted to expand the diameter of the topelectrode 103 from about 12 inches to about 19 inches, such as about 15inches to about 17 inches. The outer electrode member 107 can be acontinuous member (e.g., a poly-silicon or silicon carbide member, suchas a ring), or a segmented member (e.g., 2-6 separate segments arrangedin a ring configuration, such as segments of single crystal silicon). Inembodiments in which the top electrode 103 includes a multiple-segmentouter electrode member 107, the segments preferably have edges whichoverlap each other to protect an underlying bonding material fromexposure to plasma. The inner electrode member 105 preferably includesmultiple gas passages 104 for injecting a process gas into a space in aplasma reaction chamber below the top electrode 103. Optionally, theouter electrode member 107 can include multiple gas passages (notshown). The outer electrode 107 preferably forms a raised step at theperiphery of the electrode 103 which does not include gas passages.Further details of a stepped electrode can be found in commonly-ownedU.S. Pat. No. 6,824,627, the entire disclosure of which is herebyincorporated by reference.

Single crystal silicon is a preferred material for plasma exposedsurfaces of the inner electrode member 105 and the outer electrodemember 107. High-purity, single crystal silicon minimizes contaminationof substrates during plasma processing as it introduces only a minimalamount of undesirable elements into the reaction chamber, and also wearssmoothly during plasma processing, thereby minimizing particles.

The showerhead electrode assembly 100 can be sized for processing largesubstrates, such as semiconductor wafers having a diameter of 300 mm.For 300 mm wafers, the top electrode 103 is at least 300 mm in diameter.However, the showerhead electrode assembly can be sized to process otherwafer sizes or substrates having a non-circular configuration such assubstrates for flat panel displays.

The backing member 102 includes a backing plate 106 and optionally abacking ring 108. In such configurations, the inner electrode member 105is co-extensive with the backing plate 106, and the outer electrodemember 107 is co-extensive with the surrounding backing ring 108.However, the backing plate 106 can extend beyond the inner electrodemember such that a single backing plate can be used to support the innerelectrode member and the segmented outer electrode member or support asingle piece inner electrode and outer electrode. The inner electrodemember 105 and the outer electrode member 107 are preferably attached tothe backing member 102 by a bonding material, such as an elastomericbonding material. The backing plate 106 includes gas passages 113aligned with the gas passages 104 in the inner electrode member 105 toprovide gas flow into the plasma processing chamber. If the outerelectrode 107 includes gas passages, the backing ring 108 includes gaspassages aligned with such optional gas passages in the outer electrode107 (not shown). The gas passages 113 can typically have a diameter ofabout 0.04 inch, and the gas passages 104 can typically have a diameterof about 0.025 inch.

In the embodiment, the backing plate 106 and backing ring 108 are madeof an aluminum material, which is typically an aluminum alloy materialsuch as 6061 or other alloy suitable for use in semiconductorprocessing. The backing plate 106 and backing ring 108 can be made ofbare aluminum, i.e., aluminum that has a surface native oxide (and isnot anodized).

The top electrode 103 can be attached to the backing plate 106 andbacking ring 108 with a thermally and electrically conductive elastomerbonding material that accommodates thermal stresses, and transfers heatand electrical energy between the top electrode 103 and the backingplate 106 and backing ring 108. Alternatively, the elastomer can bethermally conductive, but not electrically conductive. The use ofelastomers for bonding together surfaces of an electrode assembly isdescribed, for example, in commonly-owned U.S. Pat. No. 6,073,577, whichis incorporated herein by reference in its entirety.

The backing plate 106 and the backing ring 108 are preferably attachedto the thermal control plate 101 with suitable fasteners, which can bethreaded bolts, screws, or the like. For example, bolts (not shown) canbe inserted in holes in the thermal control plate 101 and screwed intothreaded openings in the backing member 102. The thermal control plate101 is in heat transfer relationship with an actively controlled heater.See, for example, FIGS. 1 and 2 and the description thereof incommonly-owned U.S. Published Application No. 2005/0133160A1, the entiredisclosure of which is hereby incorporated by reference. The holes inthe thermal control plate 101 can be oversized to allow for movement dueto differences in thermal expansion that accommodates thermal stresses.The thermal control plate 101 includes a flexure portion 109 and ispreferably made of a machined metallic material, such as aluminum, analuminum alloy such as aluminum alloy 6061 or other alloy suitable foruse in semiconductor processing. The thermal control plate 101 can bemade of bare aluminum, i.e., aluminum that has a surface native oxide(and is not anodized). The top plate 111 is preferably made of aluminumor an aluminum alloy such as aluminum alloy 6061. A plasma confinementassembly 110 is shown outwardly of the showerhead electrode assembly100. A suitable plasma confinement assembly including avertically-adjustable, plasma confinement ring assembly is described incommonly-owned U.S. Pat. No. 6,433,484, which is incorporated herein byreference in its entirety.

The thermal control plate 101 preferably includes at least one heateroperable to cooperate with the temperature-controlled top plate 111 tocontrol the temperature of the top electrode 103. For example, in apreferred embodiment, the heater is provided on the upper surface of thethermal control plate 101 and includes a first heater zone surrounded bya first projection 61, a second heater zone between the first projection61 and a second projection 63, and a third heater zone between thesecond projection 63 and the flexure portion 109. The number of heaterzones can be varied; for example, in other embodiments the heater caninclude a single heater zone, two heater zones, or more than threeheater zones. The heater can alternatively be provided on a bottomsurface of the thermal control plate.

The heater preferably comprises a laminate including a resistivelyheated material disposed between opposed layers of a polymeric materialthat can withstand the operating temperatures reached by the heater. Anexemplary polymeric material that can be used is a polyimide sold underthe trademark Kapton®, which is commercially available from E.I. du Pontde Nemours and Company. Alternatively, the heater can be a resistiveheater embedded in the thermal control plate (e.g., a heating element ina cast thermal control plate or a heating element located in a channelformed in the thermal control plate). Another embodiment of the heaterincludes a resistive heating element mounted on the upper and/or lowersurface of the thermal control plate. Heating of the thermal controlplate can be achieved via conduction and/or radiation.

The heater material can have any suitable pattern that provides forthermally uniform heating of the first heater zone, second heater zone,and third heater zone. For example, the laminate heater can have aregular or non-regular pattern of resistive heating lines such as azig-zag, serpentine, or concentric pattern. By heating the thermalcontrol plate with the heater, in cooperation with operation of thetemperature-controlled top plate, a desirable temperature distributioncan be provided across the top electrode during operation of theshowerhead electrode assembly.

The heater sections located in the first heater zone, second heaterzone, and third heater zone can be secured to the thermal control plateby any suitable technique, e.g., the application of heat and pressure,adhesive, fasteners, or the like.

The top electrode can be electrically grounded, or alternatively can bepowered, preferably by a radio-frequency (RF) current source 170. Theoutput power of the RF current source 170 powering the top electrode canhave a frequency ranging from 50 to 80 MHz, preferably a frequency of 60MHz, or a similar frequency. In such an alternative embodiment, thebottom electrode can be coupled to the ground potential and the topelectrode coupled to the RF source 170. The RF source 170 can have avoltage of between about 100 volts and about 2000 volts. In a preferredembodiment, the top electrode is grounded, and power at one or morefrequencies is applied to the bottom electrode to generate plasma in theplasma processing chamber. The RF source 170 powering the bottomelectrode can have a frequency of between about 400 kHz and about 60MHz. For example, the bottom electrode can be powered at frequencies of2 MHz and 27 MHz by two independently controlled radio frequency powersources.

After a substrate has been processed (e.g., a semiconductor substratehas been plasma etched), the supply of power to the bottom electrode isshut off to terminate plasma generation. The processed substrate isremoved from the plasma processing chamber, and another substrate isplaced on the substrate support for plasma processing. In a preferredembodiment, the heater is activated to heat the thermal control plate101 and, in turn, the top electrode 103, when power to the bottomelectrode is shut off. As a result, the top electrode 103 temperature ispreferably prevented from decreasing below a desired minimumtemperature. For etching dielectric materials, the top electrodetemperature is preferably maintained at approximately a constanttemperature such as 150 to 250° C. between successive substrateprocessing runs so that substrates are processed more uniformly, therebyimproving process yields. The power supply preferably is controllable tosupply power at a desired level and rate to the heater based on theactual temperature and the desired temperature of the top electrode.

In exemplary embodiments, the top electrode 103 can be heated to atemperature of at least about 80° C., such as heating and maintaining atleast a portion of the showerhead electrode at a temperature of at least100° C., at least about 150° C., or at least 180° C. The top electrode103 can be heated before etching of a semiconductor substrate. Theetching can comprise etching openings in an oxide layer on thesemiconductor substrate, where the openings are defined by a patternedphotoresist.

The plasma chamber can also include, for example, a temperaturecontroller; a power supply adapted to supply power to a heater whichheats the thermal control plate in thermal response to the temperaturecontroller; a fluid control adapted to supply fluid to a temperaturecontrolled top wall of the chamber in response to the temperaturecontroller; and a temperature sensor arrangement adapted to measure thetemperature of one or more portions of the showerhead electrode andsupply information to the temperature controller.

The illustrated embodiment of the showerhead electrode assembly alsocomprises an aluminum baffle ring arrangement 120 used to distributeprocess gasses in a plasma chamber. The aluminum baffle ring arrangement120 in FIG. 1 includes six rings made from aluminum or an aluminumalloy, such as 6061 aluminum, which comprises by weight from about 96 toabout 98% Al, about 0.8 to about 1.2% Mg, about 0.4 to about 0.8% Si,about 0.15 to 0.4% Cu, about 0.04 to 0.35% Cr, and optionally Fe, Mn, Znand/or Ti. The baffle rings 120 can have an anodized outer surface. Thesix concentric L-shaped rings are located within the plenums above thebacking member 102 and below the thermal control plate 101. For example,a central plenum can include a single ring, the adjacent plenum caninclude two rings separated by a ½ to 1 inch gap, the next adjacentplenum can include two rings separated by a ½ to 1 inch gap and an outerplenum can include a single ring. The rings are mounted to the thermalcontrol plate 101 with screws. For example, each ring can includecircumferentially spaced apart stand-offs or bosses with through holesfor receiving the screws, e.g., three bosses arranged apart can be used.Each ring can have a horizontal section of about 0.040 inch thicknessand a vertical flange of about ¼ inch in length.

When the top surface 134 of the aluminum backing plate 106 and anannular projection 136 of the thermal control plate 101 come intocontact in a contact region 132 during operation of the showerheadelectrode assembly 100, galling can occur between the thermal controlplate 101 and the aluminum backing member 102 including the backingplate 106 and backing ring 108 along contact regions located betweenthem. Details of galling are described in commonly-owned co-pending U.S.patent application Ser. No. 11/896,375, the entire contents of which arehereby incorporated by reference. In the thermal control plate 101, thecontact regions 132 can cover about 1% to about 30% of the surface areaof the backing plate 102.

This galling can occur on both of the thermal control plate 101 andaluminum backing member 102, and is caused by relative motion andrubbing occurring between the opposed surfaces of the thermal controlplate 101 and aluminum backing member 102 as a result of temperaturecycling. This galling is highly undesirable for a number of reasons.First, galling can cause a reduction in thermal transfer and thus ashift in the temperature including, for example, a localized temperaturenon-uniformity, of the top electrode 103 including the illustrated innerelectrode member 105. This temperature shift can cause a process shiftduring processing of semiconductor substrates in the plasma processingchamber.

Galling of the thermal control plate 101 and aluminum backing member 102can also cause particle generation, or cause fusing of the thermalcontrol plate 101 and aluminum backing member 102, which then requiresexcessive force to separate these components, which can result in damageto these components.

Galling of the thermal control plate 101 and aluminum backing member 102can also increase the difficulty of cleaning the top electrode 103.

Additionally, galling of the thermal control plate 101 and aluminumbacking member 102 degrades the cosmetic appearance of these componentsand reduces their lifetime.

FIG. 2 illustrates an exemplary embodiment of the showerhead electrodeassembly including a modification that reduces the occurrence of gallingof the thermal control plate 101 and aluminum backing plate 106 andbacking ring 108 and consequently also reduces problems associated withsuch galling. Particularly, as shown in FIG. 2, an interface member 151which comprises a thermally and electrically conductive gasket 145 andparticle mitigating seal portions 147 a and 147 b, is located betweenthe bottom surface of the annular projection 136 of the thermal controlplate and the top surface 134 of the aluminum backing plate 102.

FIG. 3 shows a cross-section of a portion of an embodiment of aninterface member 151. As depicted, the interface member 151 comprises athermally and electrically conductive gasket portion 145 bounded on aperiphery 149 by a particle mitigating seal portion 147 a. In thisembodiment, the gasket portion 145 preferably comprises a laminate ofcoaxial annular rings such as a central portion 143 sandwiched betweenupper and lower portions 141 a and 141 b. For example, the centralportion 143 can be a strip of aluminum and the upper and lower portions141 a/141 b can be strips of carbon loaded silicone. Alternatively, thegasket portion 145 is a thermal filler material such as a siliconefilled with boron nitride (such as CHO-THERM 1671 manufactured byChomerics), a graphite (such as eGraf 705 manufactured by Graftech), anindium foil, a sandwich (such as Q-pad II by Bergquist), or a phasechange material (PCM) (such as T-pcm HP105 by Thermagon).

The thermally and electrically conductive gasket portion 145 can be, forexample, a conductive silicone-aluminum foil sandwich gasket structure,or a elastomer-stainless steel sandwich gasket structure. In a preferredembodiment, the gasket 145 is Bergquist Q-Pad II composite materialsavailable from The Bergquist Company, located in Chanhassen, Minn. Thesematerials comprise aluminum coated on both sides withthermally/electrically conductive rubber. The materials are compatiblein vacuum environments. The contact surfaces of the thermal controlplate and aluminum backing member, e.g., backing plate, each have somedegree of roughness caused by processing, e.g., machining. The gasketmaterial is preferably also sufficiently compliant so that itcompensates for surface roughness of the contact surface and effectivelyfills regions (e.g., microvoids) of the contact surfaces to enhancethermal contact between the contact surfaces. Most preferably, thegasket portion is Lambda Gel COH-4000 (available from Geltec).

To minimize graphite generation from the gasket material, the gasketscan be cleaned using deionized water, such as by wiping. The gasketmaterial can alternatively be coated with a suitable coating material,such as a fluoroelastomer material.

The particle mitigating seal portion 147 a/147 b can be an elastomer ora polymer resistant to erosion from radicals in a vacuum environment.Preferably, the seal portion 147 a/147 b is an in-situ cured elastomeror polymer resistant to erosion from radicals produced by plasma in avacuum environment and resistant to degradation at high temperaturessuch as above 200° C. Polymeric materials which can be used in plasmaenvironments above 160° C. include polyimide, polyketone,polyetherketone, polyether sulfone, polyethylene terephthalate,fluoroethylene propylene copolymers, cellulose, triacetates, silicone,and rubber.

More preferably, the seal portion 147 a/147 b is an in-situ roomtemperature vulcanized (RTV) unfilled silicone exhibiting appropriatepre-cure and post-cure properties such as adhesion strength, elasticmodulus, erosion rate, temperature resistance and the like. For example,an in-situ curable silicone can be a two-part or one-part curing resinusing platinum, peroxide or heat. Preferably, the silicone elastomermaterial has a Si—O backbone with methyl groups (siloxane). However,carbon or carbon-fluorine backbones can also be used. Most preferably,the silicone material cures in-situ for isolating the thermally andelectrically conductive gasket portion 145 from the vacuum environmentin the chamber forming an unfilled, cross-linked silicone rubber. Anespecially preferred elastomer is a polydimethylsiloxane containingelastomer such as a catalyst cured, e.g. Pt-cured, elastomer availablefrom Rhodia as Rhodorsil V217, an elastomer which is stable attemperatures of 250° C. and higher.

The thermally and electrically conductive gasket 145 is made of amaterial that is electrically conductive (to provide an RF path to theelectrode) and thermally conductive to provide electrical and thermalconduction between the thermal control plate 101 and the aluminumbacking plate 106. The gasket 145 provides an electrically-conductivethermal interface. The gasket 145 also enhances heat transfer betweenthe top electrode 103 including the inner electrode member 105 and thethermal control plate 101. The particle mitigating seal portion 147a/147 b can be dip coated, molded, spray coated or the like onto theperiphery 149 of the thermally and electrically conductive gasketportion 145.

Preferably, the seal portion 147 a/147 b is spray coated onto theperiphery 149 of the gasket portion 145. Spray coating can result in themitigating seal portion 147 a/147 b having various cross-sectionalshapes (profiles), for example, FIG. 3 shows a mitigating seal portion147 a/147 b having a rounded-rectangular cross section. If desired, thegasket portion 145 can be in the shape of an annular ring having anoutward perimeter and an inward aperture where the particle mitigatingseal portion 147 a and 147 b, respectively, is bonded to the gasketportion 145. FIG. 4 shows a plan view of an embodiment of an interfacemember 151 comprising the gasket portion 145 shaped as an annular ringwith the seal portion 147 a bonded to the outward perimeter 149 and theseal portion 147 b bonded to the inner aperture 155. Bolt holes 157 arealso shown in FIG. 4, which allow bolts (not shown) to be inserted inholes in the thermal control plate 101 and screwed into threadedopenings in the backing plate 106 and backing ring 108 with theinterface member 151 located between the bottom surface of the annularprojection 136 of the thermal control plate and the top surface 134 ofthe aluminum backing plate 102.

Also preferably, as shown in FIG. 5A, the seal portion 147 a/147 b canbe in the form of uncured elastomeric sheets 147 c/147 d/147 e/147 f inthe shape of annular rings sized to overlap the outward perimeter andthe inward aperture of the gasket portion 145. The uncured elastomericsheets 147 c/147 d/147 e/147 f can be located on the gasket portion 145(FIG. 5B) and cured to provide an interface member 151 (FIG. 5C).

As shown in FIG. 2, the particle mitigating seals 147 a/147 b can beshaped such as O-rings disposed on the outer and inner periphery 149 ofeach annular gasket portion 145. More generally, (with reference toFIGS. 2 and 4) the particle mitigating seal portions 147 a/147 b of theinterface member 151 can have a curved surface and protrude from theoutward perimeter 153 and inward aperture 155 of each thermally andelectrically conductive gasket portion 145. A plurality of annularprojections 136 and annular thermally and electrically conductive gasketportions 145 result in a plurality of seals 147 a/147 b, for example,from 4 to 20 seal portions 147 a/147 b. The plurality of annular gasketportions 145 require fairly precise placement. Since the interfacemember 151 provides the particle mitigating seal portions 147 a/147 bbonded to the periphery 149 of the gasket portion 145, installation ofthe interface member 151 simplifies precise installation of a thermallyand electrically conductive gasket portion 145 sealed off from thevacuum chamber by particle mitigating seal portions 147 a/147 b.Particularly, when the contact surfaces of the annular gaskets 145 incontact regions 132 are small to allow for variations in location duringinstallation.

As also shown in FIG. 2, shims 146 having about the same thickness asthe gasket 145 are located between the aluminum baffle rings 120 and thebottom surface 142 of the thermal control plate 101. The shims 146 canbe of a dielectric material.

The thermal control plate 101 includes several annular projections 136establishing plenums at the backside of the backing plate 106, e.g., 2to 10, preferably 4 to 8 projections. An interface member 151 isarranged over the contact surfaces of each annular projection.

FIG. 6 shows another embodiment of an interface member 151′ locatedbetween the bottom surface of the annular projection 136 of the thermalcontrol plate and the top surface 134 of the aluminum backing plate 102.As depicted, this embodiment of an interface member 151′ has a thermallyand electrically conductive gasket portion 145′ bounded on eachperiphery by a particle mitigating portion 147 a′/147 b′. For example,the interface member 151′ shown in FIG. 6 has an annular thermally andelectrically conductive gasket portion 145′ bounded on an outerperimeter by a first co-planar particle mitigating seal portion 147 a′and bounded on an inner aperture by a second co-planar particlemitigating seal portion 147 b′. Such an embodiment of a showerheadelectrode assembly including the interface member 151′ has a fewernumber of parts than required if installing a plurality of separatethermally and electrically conductive gaskets and a separate outer andinner seal such as an O-ring, for each thermally and electricallyconductive gasket. The interface member 151′ is easy to install andcompletely covers contact regions 132. A plurality of fasteners (such as3 to 15 bolts) pass through openings 157 (FIG. 4) in each of the annulargasket portions 145/145′ to secure the thermal control plate 101 to thebacking plate 106. Furthermore, by using an interface member 151′,baffles 120 and shims 146 can be omitted if desired.

By enhancing thermal transfer through the contact regions 132, it ispossible to reduce temperature differences between the top electrode 103including the inner electrode member 105 and the thermal control plate101, such that “first wafer effects” can also be reduced duringconsecutive processing of a series of wafers. That is, “first wafereffects” refers to secondary heating of subsequent wafers causedindirectly by the heating of the first-processed wafer. Specifically,upon completion of processing of the first wafer, the heated processedwafer and the process chamber side walls radiate heat toward the upperelectrode. The upper electrode then indirectly provides a secondaryheating mechanism for subsequent wafers that are processed in thechamber. As a result, the first wafer processed by the system mayexhibit a larger than desired critical dimension (CD) variation thansubsequent wafers processed by the system since wafer temperaturevariation can affect CD during etching of high aspect ratio contact viasin semiconductor substrates. Subsequently processed wafers may havedifferent and/or less CD variation than the first processed wafer due tostabilization of temperature in the chamber.

Across-wafer and wafer-to-wafer temperature variation can also bepreferably reduced by enhancing thermal transfer through the contactregions 132. Also, chamber-to-chamber temperature matching can bepreferably achieved where multiple plasma etching chambers in differentprocessing lines are used for a desired process or throughput, byenhancing thermal transfer through the contact regions 132.

Typically, a one degree Centigrade variation in wafer temperatureacross-wafer, wafer-to-wafer, or chamber-to-chamber, can cause a CDvariation increase at 3σ (3× standard deviation) by about 0.5 to 0.1 nm(e.g., 0.4 nm/° C.-0.2 nm/° C. or 0.35 nm/° C.-0.25 nm/° C.).

As mentioned, after the first wafer has been processed, the temperatureof subsequently processed wafers can stabilize, such that temperaturevariation of reference points on subsequently processed wafers ispreferably less than about 10° C., more preferably, less than about 5°C., such that, for example, the CD variation can be controlled to withinabout 5 nm (0.5 nm/° C.×10° C.), more preferably, to within about 3 nm(0.3 nm/° C.×10° C.), most preferably to within about 0.5 nm (0.1 nm/°C.×5° C.) for etching high aspect ratio contact vias in semiconductorsubstrates.

For memory applications the CD variation is desirably less than 4 nm at3σ. With the enhanced thermal transfer through the contact regions 132provided by the interface members 151/151′, the CD variation ispreferably, 1 nm or less wafer-to-wafer and 4 nm or lesschamber-to-chamber. For logic applications the CD variation is desirablyless than 3 nm at 3σ. With the enhanced thermal transfer through thecontact regions 132 provided by the interface members 151/151′, the CDvariation is preferably, 2 nm or less wafer-to-wafer and 4 nm or lesschamber-to-chamber.

Preferably, the interface members 151/151′ minimize temperature shiftsfrom the center of the electrode to the edge of the electrode by lessthan 10° C. and minimize azimuthal temperature shifts to 5° C. or less.Electrode temperature variation due to use of new or used aluminumbacking members is related to the contact surface condition of the newand used aluminum backing members. The interface members 151/151′preferably can minimize electrode temperature shifts caused by new andused aluminum backing members to less than about 5° C. Also, parts maybe removed to be cleaned and it is preferred that a part shows the samethermal performance after such cleaning. The interface members 151/151′preferably minimize thermal performance shifts between before and aftercleaning of the aluminum backing members to less than about 5° C. changein electrode temperature.

Preferably, the interface members 151/151′ can also reduce or preventfusing or galling of the thermal control plate 101 and aluminum backingmember 102, which allows these components to be separated from eachother with minimum force.

Preferably, the interface members 151/151′ are made of a material thatpreferably: does not outgas in a high-vacuum environment of, e.g., about10 to about 200 mTorr; has low particulate generation performance; iscompliant to accommodate shear at contact regions; is free of metalliccomponents that are lifetime killers in semiconductor substrates, suchas Ag, Ni, Cu and the like; and can minimize the generation of particlesduring cleaning of the aluminum backing member 102.

FIG. 7 illustrates a portion of another embodiment of a showerheadelectrode assembly. Referring to FIGS. 2 and 6, the embodiment shown inFIG. 7 does not include a backing member, and the thermal control plate101 is secured directly to the inner electrode member 105.

When the top surface 160 of the top electrode 103 and an annularprojection 136 of the thermal control plate 101 come into contact in acontact region 158 during operation of the showerhead electrode assembly100, galling can occur between the thermal control plate 101 and the topelectrode 103 including the inner electrode member 105 and the optionalouter electrode member 107 along contact regions located between them.

This galling can occur on both of the thermal control plate 101 and thetop electrode 103, and is caused by relative motion and rubbingoccurring between the opposed surfaces of the thermal control plate 101and the top electrode 103 as a result of temperature cycling. Thisgalling is undesirable for reasons similar to those described above inrelation to the top surface 134 of the aluminum backing plate 106 and anannular projection 136 of the thermal control plate 101 contacting in acontact region during operation of the showerhead electrode assembly100. For example, galling can cause a reduction in thermal transfer andthus a shift in the temperature including, for example, a localizedtemperature non-uniformity, of the top electrode 103 including theillustrated inner electrode member 105. This temperature shift can causea process shift during processing such as plasma etching ofsemiconductor substrates in the plasma processing chamber.

Galling of the thermal control plate 101 and the top electrode 103 canalso cause particle generation, or cause fusing of the thermal controlplate 101 and the top electrode 103, which then requires excessive forceto separate these components, which can result in damage to thesecomponents. Galling of the thermal control plate 101 and the topelectrode 103 can also increase the difficulty of cleaning the topelectrode 103. Additionally, galling of the thermal control plate 101and the top electrode 103 degrades the cosmetic appearance of thesecomponents and reduces their lifetime.

The showerhead electrode assembly shown in FIG. 7 can also include anoptional outer electrode member, such as the outer electrode member 107shown in FIG. 1. The outer electrode member can have a ringconfiguration comprised of a plurality of segments. The thermal controlplate 101 can be secured directly to the inner electrode member 105 andoptional outer electrode member 107 in any suitable manner, such as byfasteners and/or adhesive bonding, such as elastomer bonding. As shownin FIG. 7, there is a contact region 158 between the top surface 160 ofthe inner electrode member 105 and the annular projection 136 of thethermal control plate 101. In the embodiment, the outer surface of thethermal control plate 101 can be anodized except at the surface at thecontact region 158, which is of bare aluminum (non-anodized). Contactregion 158 provides a thermal path to remove heat from the innerelectrode member 105 and an RF path for RF power passing through theinner electrode member 105.

An interface member 151 such as described above with reference to FIG. 2is provided between the top surface 160 of the inner electrode member105 and the annular projection 136 of the thermal control plate 101. Asdescribed above, thermally and electrically conductive gasket portion145 provides a thermal path to remove heat from the inner electrodemember 105 and an RF path for RF power passing through the innerelectrode member 105. Particle mitigating seal portions 147 a/147 b arebonded to the gasket portion 145 and are disposed in offsets 139 betweenthe aluminum baffle rings 120 and the top surface 160 to form agas-tight seal. The upper ends of the vertical walls of the baffle rings120 are separated from the bottom surface 142 of the thermal controlplate 101 by shims 146. The shims 146 are typically made of a dielectricmaterial, such as Kapton®.

FIG. 8 illustrates an embodiment of an interface member 151′ in ashowerhead electrode assembly to reduce the occurrence of gallingbetween the thermal control plate 101 and the inner electrode member 105(and also the optional outer electrode member) along contact regionslocated between them, and consequently to also reduce problemsassociated with such galling, such as particle generation. For example,for a silicon electrode member, galling can cause silicon particlegeneration and aluminum particle generation. Particularly, as shown inFIG. 8, the interface member 151′ is located between the bottom surfaceof the annular projection 136 of the thermal control plate 101 and thetop surface 160 of the inner electrode member 105. The interface member151′ separates adjacent ones of the plenums formed in the thermalcontrol plate 101 from each other.

The interface member 151′ can be made of the same materials as theinterface members 151/151′ described above with respect to theembodiment of the showerhead electrode assembly shown in FIGS. 6 and 7.The gasket portion 145′ material is electrically and thermallyconductive to provide electrical and thermal conduction between thethermal control plate 101 and the inner electrode member 105 (andoptional outer electrode member), i.e., the gasket 145′ provides anelectrically-conductive thermal interface between the contact regions.

As also shown in FIG. 8, shims 146 having about the same thickness asthe interface member 151′ are located between the aluminum baffle rings120 and the bottom surface 142 of the thermal control plate 101. Theshims 146 can be of a dielectric material. The interface member 151′allows the aluminum baffles 120 and shims 146 to be omitted if desired.

The modification to the showerhead electrode assemblies shown in FIGS. 2and 6-8 reduce the number of parts, simplify installation and completelycover contact regions 132/158, as well as, reduce the occurrence ofgalling between the thermal control plate 101 and the inner electrodemember 105 (and also the optional outer electrode member) along contactregions 132/158 located between them, and consequently also reduceproblems associated with such galling, such as particle generation. Forexample, for a silicon electrode member, galling can cause siliconparticle generation and aluminum particle generation. Particularly, asshown in FIG. 8, an interface member 151′ is located between the bottomsurface of the annular projection 136 of the thermal control plate 101and the top surface 160 of the inner electrode member 105. The interfacemember 151′ separates adjacent ones of the plenums formed in the thermalcontrol plate 101 from each other.

While the invention has been described in detail with reference tospecific embodiments thereof, it will be apparent to those skilled inthe art that various changes and modifications can be made, andequivalents employed, without departing from the scope of the appendedclaims.

1. (canceled)
 2. The showerhead electrode assembly of claim 18, whereinthe contact regions comprise spaced apart annular projections on a lowersurface of the thermal control plate, the interface members comprising aplurality of annular interface members sized to cover the annularprojections, the particle mitigating seal portion bounding the thermallyand electrically conductive gasket portion at an outward perimeter andan inward aperture of each interface member.
 3. The showerhead electrodeassembly of claim 2, wherein the particle mitigating seal portionlocated at the outward perimeter has a curved surface and protrudes fromthe electrically conductive gasket portion and the particle mitigatingseal portion located at the inward aperture has a curved surface andprotrudes from the thermally and electrically conductive gasket portion.4. The showerhead electrode assembly of claim 18, wherein the thermalcontrol plate is of non-anodized aluminum, the thermally andelectrically conductive gasket portion of the interface member is alaminate of metal and polymer materials, and the particle mitigatingseal portion of the interface member comprise an erosion resistantelastomer or polymer.
 5. The showerhead electrode assembly of claim 18,wherein the showerhead electrode comprises an inner electrode and anouter electrode, and the inner electrode is a circular plate of singlecrystal silicon and the outer electrode is a ring electrode comprised ofa plurality of segments of single crystal silicon.
 6. The showerheadelectrode assembly of claim 3, further comprising baffle rings ofanodized aluminum in plenums between the annular projections, eachbaffle ring including a vertical wall adjacent one of the annularprojections, the vertical walls including offsets at lower ends thereofadjacent the contact regions, and each particle mitigating seal portionlocated in one of the offsets so as to form seals on opposite sides ofthe contact regions.
 7. (canceled)
 8. The showerhead electrode assemblyof claim 6, wherein upper ends of the vertical walls of the baffle ringsare separated from a lower surface of the thermal control plate by shimshaving about the same thickness as the thermally and electricallyconductive gasket portion of the interface member.
 9. The showerheadelectrode assembly of claim 18, further comprising thermal chokes on anupper surface of the thermal control plate.
 10. The showerhead electrodeassembly of claim 18, wherein the interface member is free of silver,nickel and copper, and the contact regions cover about 1% to about 30%of the surface area of the backing plate.
 11. A vacuum chambercomprising the showerhead electrode assembly of claim 18, furthercomprising: a temperature controller controlling a temperature of ashowerhead electrode assembly; a power supply adapted to supply power toa heater which heats the thermal control plate in thermal response tothe temperature controller; a fluid control adapted to supply fluid to atemperature controlled top wall of the chamber in response to thetemperature controller; and a temperature sensor arrangement adapted tomeasure the temperature of one or more portions of the showerheadelectrode and supply information to the temperature controller, whereinthe top wall of the vacuum chamber is optionally electrically grounded.12. The showerhead electrode assembly of claim 18, wherein theshowerhead electrode includes a silicon electrode plate with gas outletson one side thereof and the opposite side thereof elastomer bonded to abacking plate which is of non-anodized aluminum.
 13. A method ofcontrolling plasma etching in a plasma etching chamber, comprising:supplying process gas to the plasma etching chamber through theshowerhead electrode assembly of claim 18, the process gas flowing intoa gap between the showerhead electrode and a bottom electrode on which asemiconductor substrate is supported; and etching a semiconductorsubstrate in the plasma etching chamber by applying RF power to theshowerhead electrode and energizing the process gas into a plasma state,wherein the temperature of the showerhead electrode is controlled by thethermal control plate via enhanced thermal conduction through thethermally and electrically conductive gasket portion of the interfacemembers.
 14. The method of claim 13, further comprising heating of theshowerhead electrode to a temperature of at least about 80° C.
 15. Themethod of claim 14, wherein the heating of the showerhead electrodecomprises heating and maintaining the showerhead electrode at atemperature of at least about 100° C.
 16. The method of claim 14,wherein the heating of the showerhead electrode comprises heating andmaintaining the showerhead electrode at a temperature of at least about180° C.
 17. The method of claim 13, wherein the heating of theshowerhead electrode occurs before the etching of the semiconductorsubstrate, and the etching comprises etching openings defined by apatterned photoresist in an oxide layer on the semiconductor substrate,the openings being defined by a patterned photoresist.
 18. A showerheadelectrode assembly, comprising: a showerhead electrode adapted to bemounted in an interior of a vacuum chamber; a thermal control plateattached to the showerhead electrode at multiple contact regions acrossthe showerhead electrode with plenums between the thermal control plateand the showerhead electrode located between the contact regions; andinterface members between the showerhead electrode and the thermalcontrol plate, at the contact regions, wherein each interface membercomprises a thermally and electrically conductive gasket portion boundedon a periphery by a particle mitigating seal portion.
 19. The showerheadelectrode assembly of claim 18, wherein: the contact regions comprisesurfaces of spaced-apart annular projections provided on a lower surfaceof the thermal control plate, the contact regions cover about 1% toabout 30% of the surface area of the backing plate; the interfacemembers comprise an annular interface member located between each of theannular projections and an upper surface of the electrode; the thermallyand electrically conductive gasket portion of the interface members arecomposed of a laminate of metal and polymer materials free of silver,nickel and copper; and the particle mitigating seal portion of theinterface members bound an outer perimeter and an inner aperture of eachthermally and electrically conductive gasket portion, and are comprisedof silicone.
 20. The showerhead electrode assembly of claim 19, wherein:the showerhead electrode comprises an inner electrode and an outerelectrode, the inner electrode is a circular plate of single crystalsilicon and the outer electrode is a ring electrode comprised of aplurality of segments of single crystal silicon; the particle mitigatingseal portions of the interface members have a curved surface andprotrude from the outward perimeter and inward aperture of eachthermally and electrically conductive gasket portion; and the showerheadelectrode assembly further comprises: baffle rings of anodized aluminumin plenums between the annular projections, each baffle ring including avertical wall adjacent one of the annular projections, the verticalwalls including offsets at lower ends thereof adjacent the contactregions; and the particle mitigating seal portions located in theoffsets so as to form seals on opposite sides of the contact regions,wherein upper ends of the vertical walls of the baffle rings areseparated from a lower surface of the thermal control plate by shimshaving about the same thickness as the thermally and electricallyconductive gasket portions of the interface members.
 21. The showerheadelectrode assembly of claim 19, wherein the thermal control plate has ananodized outer surface except at the contact regions which are ofnon-anodized aluminum.